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Joint:Wrist joint:Capsule
Summary * Ligaments run obliquely; from periphery to midline; from proximal to distal * Volar ligaments are key stabilizers; dorsal ligaments, less crucial * Capitate & lunate have most ligament attachments * Triquetrum is ulnar anchor for capsular ligaments * All adjacent carpals have interosseous ligaments: Medial/lateral, distal/proximal (except lunate & capitate - no proximal/distal ligament) Volar Radiocarpal Ligaments * Radioscaphocapitate (sling, radiocapitate) ** Origin: Distal radius, radial styloid; course: Passes across scaphoid waist with minimal attachment; insertion: Capitate body (10% of fibers); arcs around distal lunate, interdigitates with UC & TC to form arcuate ligament *** Radial collateral: Radial-most fibers of RSC; existence as separate ligament debated ** Action: Constrains radiocarpal pronation, ulnocarpal translocation; stabilizes distal scaphoid pole; creates sling for scaphoid * Long radiolunate (volar radiolunotriquetral, volar radiotriquetral ligament) * Radioscapholunate (ligament of Testut; intra-articular fat pad) * Short radiolunate * Arcuate ("V" ligament): Confluence of ligaments on volar capitate including RSC, UC & TC Dorsal Radiocarpal Ligament * Dorsal radiocarpal (dorsal radiotriquetral; dorsal radiolunotriquetral) Volar Midcarpal Ligaments * Scaphotrapezium-trapezoid * Scaphocapitate * Triquetrocapitate * Triquetrohamate * Pisohamate * Deltoid: Confluence of scaphocapitate & triquetrocapitate ligaments; parallels arcuate ligament Dorsal Midcarpal Ligaments * Dorsal intercarpal ** Origin: Dorsal triquetrum, interdigitating with DRC ligament; insertion: Scaphoid & dorsal trapezoid ** Action: Envelops radial artery in anatomic snuffbox; constrains midcarpal rotation; acts as labrum to capitate head & proximal hamate * Dorsal scaphotriquetral ** Origin: Scaphoid, extending dorsal & distal to SL/LT ligaments; insertion: Dorsal triquetrum ** Action: Stabilizes SL/LT ligaments; labrum for capitate head & hamate proximal pole Proximal Interosseous Ligaments * Scapholunate ** Origin/insertion: Ulnar scaphoid to radial lunate; hyaline cartilage attachment ** Action: Dorsal portion resists volar-dorsal translation; volar portion limits flexion/extension rotation; proximal accommodates compression & shear forces across radiocarpal joint ** U-shaped ligament with dorsal, proximal & volar components *** Dorsal component thicker (5 mm) than volar (1-2 mm); functionally more important than proximal portion *** Proximal component is meniscus-like avascular fibrocartilage; triangular shape ** Attritional tears with age * Lunotriquetral ** Origin/insertion: Ulnar lunate to radial triquetrum; hyaline cartilage attachment ** Action: Volar portion limits translation of lunate & triquetrum; dorsal portion stabilizes joint ** U-shaped ligament with dorsal, proximal & volar components *** Volar component thicker (2.3 mm) than dorsal (1 mm); functionally more important than proximal portion *** Proximal component is meniscus-like avascular fibrocartilage; triangular shape ** Attritional tears with age Distal Interosseous Ligaments * Trapeziotrapezoid * Trapeziocapitate * Capitohamate Carpometacarpal Ligaments * Pisometacarpal * Carpometacarpal ligaments of thumb * Dorsal carpometacarpal * Volar carpometacarpal Distal Radioulnar Ligaments * Dorsal radioulnar ** Origin: Dorsal sigmoid notch, bone attachment; insertion: Dorsal fibers form ECU sheath & attach to styloid process; volar fibers attach to ulnar fovea ** Action: Stabilizes distal ulna, preventing volar subluxation during supination * Volar radioulnar ** Origin: Volar sigmoid notch, bone attachment; insertion: Ulnar fovea; joins with volar fibers of DRU & creates a "ring" (apparent on MR) ** Action: Serves as base for UL & UT ligament origins; stabilizes distal ulna, preventing dorsal subluxation during pronation Ulnocarpal Structures * Ulnolunate * Ulnotriquetral ** Lateral band ** Medial band (ulnar collateral ligament) *** Origin: Arises from DRU at its insertion on ulnar styloid;insertion: Lateral triquetrum *** Action: Forms floor of ECU tendon sheath; constrains distal translation of triquetrum *** Actual existence of ulnar collateral ligament is debated ** Arises from ligament rather than bone, reducing effects of forearm rotation on carpals ** Lateral & medial bands separate just distal to prestyloid recess; lead to pisotriquetral joint (in 90%) * Ulnocapitate * Ulnocarpal meniscal homologue Triangular fibrocartilage (articular disc) * Origin: Arises from radial sigmoid notch, attaching to hyaline cartilage; insertion: Ulnar fovea & styloid tip * Variable thickness proportional to ulnar length (thicker with ulnar minus, thinner with ulnar plus); ulnar portion 2-3x thicker than radial * Ulnar portion is vascularized; radial & central portions are not * Attritional tears with age * Triangular fibrocartilage complex ** Complex includes articular dorsal and volar radioulnar ligament, ulna carpal ligament (UL and UT) & ECU tendon sheath ** Action: Transmits portion of axial load from ulnar carpals to distal ulna; stabilizer of DRU joint; stabilizer of ulnar carpals